Electric valve circuit



Nov. 18, 1941. H. w. LOP-2D 2,263,306

ELECTRIC VALVE CIRCUIT Filed Ma 21, 1958 Inventor: Harold W. Lord,

by H is Atbor'n e g.

Patented Nov. 18, 1941 ELECTRIC VALVE CIRCUIT Harold W. Lord, Schenectady, General Electric Company,

New York N. Y., assignor to a corporation of Application May 21, 1938, Serial No. 209,400

18 Claims.

My invention relates to electric translating apparatus and more particularly to control systems for electric Valve circuits.

Electric valve apparatus of the type employing ionizable mediums, because of the facility with which current may be initiated and interrupted by their use, have found considerable application in those fields where it is desired to eflect periodic energization of a load circuit from an alternating current circuit, or where it is desired to effect energization of a load circuit from an alternating current circuit during an accurately determinable interval of time. Furthermore, electric valve apparatus of the type employing an ionizable medium and having a control member for initiating the arc discharge have been found particularly adaptable to circuits where it is desired to control the amount of energy transmitted to the load circuit during an interval of time.

Various control circuits have been proposed heretofore to effect the desired precision of operation and to effect positive control. For example, in the energization of the control members of electric valves of this nature, the wave form of the control member energizing voltage has been modified in an effort to effect a positive initiation of the arc discharge. For example, voltages of perpendicular wave front and of peaked wave form have been impressed on the control members to render the electric valves conductive at a precisely determinable time during half cycles of applied anode-cathode voltage. In accordance with the teachings of my invention to be described hereinafter, I provide a new and improved control system for controlling electric valve means whereby there is afforded a positive means for rendering the electric valves conductive.

It is an object of my invention to provide a new and improved electric valve circuit.

It is another object of my invention to provide new and improved electric valve translating apparatus.

It is a further object of my invention to provide a new and improved electric valve control circuit for electric valve translating apparatus.

It is a still furtherobject of my invention to provide a new and improved control system for electric valve means of the type employing an ionizable medium and which comprises high-frequency means for energizing the control members of the electric valve means.

In accordance with the illustrated embodiment of my invention, I provide a new and improved electric valvev translating circuit for transmitting power or energy from an alternating current sup ply circuit of commercial frequency to an alternating current load circuit through a pair of reversely connected electric valve means, of the ergization of the control members, or, in other words, the period of energization of the input circuit of the high-frequency oscillator, is controlled by means of a full wave rectifier which is energized from an alternating current source.

$ The full wave rectifier comprises a pair of electronic discharge devices which conduct current alternately and which transmit a rectified alternating current to the input circuit of the oscillator. The electronic discharge devices are arranged in a leading and following relationship and in order to effect energization of the load circuit during a predetermined interval of time, the leading discharge device is rendered conductive by impressing on the control member thereof a transient positive voltage suflicient to overcome the effect of a negative biasing potential which is impressed on the control member.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. The single figure of the accompanying drawing diagrammaticallyillustrates an embodiment of my invention in which the power electric valves are of the type employing external control members of the starting band type.

Referring now to the single figure of the drawing my invention is there shown as applied to an electric valve translating circuit for transmitting energy from an alternating current supply circuit I of a commercial frequency to a load circuit, such as a welding circuit 2, through a transformer 3 and a pair of reversely or inversely connected electric valve means 4 and 5.

. Electric valve means 4 and 5 are connected to transmit both half cycles of current supplied by the supply circuit l and hence to transmit alternating current to the welding circuit 2. The electric valve means 4 and 5 are preferably of the type employingan ionizable medium, such as a gas or a vapor, and each has an anode 6 and a cathode 'l. The electric valve means 4 and 5 may be of the type comprising control members 8 of the starting band type in which an are discharge is initiated between the anode 6 and the cathode 1 by impressing upon the control members 8 voltages of sufficient magnitude or having a suiliciently high rate of change.

While the electric valve means 4 and 5 have been shown as being of the type employing control members of the starting band type, it is to be understood that my invention in its broadest aspect may be applied to electric valve means generally irrespective of the nature of the control member.

In order to energize the control members 8 of the electric valve means 4 and 5, I provide a high-frequency generating means such as a high-frequency electric valve oscillator 9. The 10,

electric valve oscillator 9 comprises an electric valve In, of the high vacuum type, having a grid II, a capacitance l2 and an inductance l3 which may be a winding of a transformer l4. The electric valve Hi, the capacitance l2, the inductance l3 and capacitance 3| constitute the principal elements of the high-frequency electric valve oscillator. Transformer l4 also includes windings l5 and IS, the former of which is connected to the anode of the electric valve H1 and the latter of which is connected to the grid ll of the electric valve In. To impress on the control members 8 a steep wave front train of high-frequency electrical impulses, I introduce into the output circuit ll of the electric valve oscillator 9 a suitable means such as a spark-gap l8. The spark-gap l8 breaks down when the voltage of the oscillator 9 attains a predetermined value to impress on the control members a steep front train of high-frequency electrical 3 impulses. A suitable biasing means, such as a self-biasing circuit, comprising a parallel connected capacitance l9 and a resistance 20 is connected in series relation with winding l6 and in circuit with grid H of electric valve ID. The input circuit 2| of the oscillator 9 is energized from a circuit described hereinafter.

I have found that the electric valves 4 and 5 are controlled in a positive manner by impressing on the control members 8 a relatively high frequency alternating voltage of approximately three thousand cycles. The electric valve oscillator 9 may be designed to be adjustable so that the output voltage and the output frequency may be varied. The secondary winding l3 of transformer I4 is preferably a high voltage winding capable of supplying about six thousand volts.

It is to be understood that the design of the electric valve oscillator 9 is preferable in accordance with the break-down characteristics of the spark-gap l8. Although I have found that satisfactory operation is obtained for the above mentioned values of frequency and voltage, it

is to be understood that my invention is not limited to an arrangement employing these values but may in its broader aspects cover generally control circuits for electric valve apparatus in which a high frequency generator energizes the control members of electric valve means.

To energize the inputcircuit 2| of the electric valve oscillator 9 and hence to control the electric valve means 4 and 5, I provide a' rectifier circuit 22 which may be of the full wave type and which may comprise a pair of electronic dischargedevices 23and 24. By the term full wave is meant that type of rectifying circuit which rectifies both the positive and negative half cycles of voltage of the associated alternating current circuit. Electronic discharge devices 23 and 24 are preferably of the type employing an ionizable medium and each comprises an anode 25, .a cathode 26 and a control member or grid 21. A current limiting resistance 21' may be connected in series relationwith grid 21. A shield grid 28 may be employed, if desired. The

. rectified alternating voltage.

anode-cathode circuits of the electronic discharge devices 23 and 24 are energized from a transformer 29 and the electric valves 23 and 24, of course, are connected to conduct current alternately. The transformer 29 may be energized from any suitable source of alternating current of the proper phase and frequency and in the drawing is shown as being energized from the alternating current supply circuit I through a suitable phase shifting means, such as a rotary phase shifter 3.0. The phase shifter 30 is adjusted to impress on the anodes 25 of electronic discharge devices 23 and 24 a voltage which leads the voltage'of circuit I by an appreciable angle so that the voltage impressed on circuit 2! is of sufficient value to set the high frequency oscillator 9 into operation at the time dictated by the control circuit described hereinafter. I have found that an angle of lead of substantially 30 electrical degrees is satisfactory. The electronic discharge devices 23 and 24 are connected to the input circuit 2! of the electric valve oscillator 9 and develop across a capacitance 3i and a resistance 32 a voltage of the polarity indicated. Capacitance 3! constitutes, with the inductance l3, a tank circuit for the oscillator 9. It will be understood that the voltage appearing across capacitance 3| and resistance 32 is a The cathodes 26 of the electronic discharge devices 23 and. 24 may be energized from the supply circuit I through a cathode heating transformer33.

Electronic discharge devices 23 and 24 are arranged in a leading and following relationship. That is, the electronic discharge device 24 is arranged to follow the discharge device 23 and to conduct current during only the half cycles immediately following the half cycles of conduction of discharge device 23. This control is effected by means of a circuit including a transformer 34 which impresses onv the grid 21 of discharge device 24 an alternating potential which biases the discharge device 24 to a non- .conducting condition, or, in other words, it

maintains the device 24 nonconductive. A suitable source of negative unidirectional biasing potential is provided by a conventional means, such as a parallel connected resistance 35 and a capacitance 36, which produces the negative biasing potential by virtue of the grid rectification characteristic of the device 24. To overcome the effect of the biasing potential produced by transformer 34, resistance 35 and capacitance 3B and to render the electronic discharge device 24 conductive during thehalf cycles of voltage immediately following the half cycles of conduction of electronic discharge device 23, I provide a circuit including a suitable unidirectional conducting device 31 and a capacitance 38. The ca- 0 pacitance 38 is charged from the circuit 2| through the unidirectional conducting device 31 when the electronic discharge device 23 conducts current. The left-hand plate of the capacitance 38 becomes positive and impresses a positive voltage on grid 21 of discharge device 24 through transformer 34 and resistance 35 to render discharge device 24 conductive. A discharge circuit for capacitance 38 is provided and includes a resistance 39 which permits discharge of the capacitance 38 into the circuit 2|. This discharge circuit is proportioned so that the positive voltage produced by the capacitance 38 is not effective for an interval of time exceeding a half cycle of voltage of the alternating current circuit I. In this manner, the discharge device 24 conducts current during only those half cycles immediately following the half cycles of conduction of discharge device 23. As a means for controlling the operative period of the rectifier 22 and hence for controlling the period of energization of the input circuit 2| of the electric valve oscillator 9, I provide a control circuit 40 which comprises a source of unidirectional voltage 4|, a voltage divider comprising resistances 42, 43, 44, 45 and 46, an electric valve 41 and a serially connected capacitance 48 and a resistance 9. The electric valve means 41 is preferably of the type employing an ionizable medium, such as a gas or a vapor, and includes control member 50. A current limiting resistance 50' may be connected in series relation with control member 50. The serially connected capacitance 48 and resistance 49 are connected to be energized in accordance with the voltage appearing across the serially connected resistances 42, 43 and 44. Electric valve 41 when in a conducting condition short circuits the resistance 45 and hence effects the transmission of a larger amount of current through the other resistances of the voltage divider. A resistance 5| is connected across the anode and cathode of the elec tric valve 41 and a suitable circuit controlling means, such as a switch 52, is connected in circuit with the cathode of electric valve 41 and one terminal of the resistance 46.

To render the electric valve 41 conductive at a predetermined time during the cycles of voltage of circuit I and hence to initiate energization of the welding circuit 2 at a predetermined time, I provide a suitable means for impressing on the control member 50 of electric valve 41 a voltage of perpendicular wave front or of peaked wave form. I have shown for efiecting this control a conventional arrangement comprising a transformer 53, which may be of the satura'cle type and which comprises a core member 54. a primary winding 55 and a secondary Winding 56 in which there is induced an alternating voltage of peaked wave form. A suitable phase shifting arrangement, such as a rotary phase shifter 51, may be employed to control the phase of the voltage of peaked wave form produced by winding 56. A negative unidirectional biasing potential is impressed on the control member 50 of electric valve 41 and may be derived from the voltage divider, particularly resistance 46 thereof. When the switch 52 is in the open circuit position, electric valve 41, of course, is inoperative and when the switch 52 is in the closed circuit position the electric valve is maintained nonconductive by the negative biasing potential until the occurrence of the voltage of peaked wave form.

Although I have chosen to show the electronic discharge devices 23 and 24 as being arranged to have a leading and following relationship, it

is to be understood that I may employ a control circuit in which both electronic discharge devices 23 and 24 are directly controlled by the circuit 40. Where electronic discharge device 24 is arranged to follow discharge device 23, it is to be understood that an even number of half cycles of current will be transmitted to the welding circuit 2. However, if both electronic discharge devices 23 and 24 are directly controlled by circuit 40, it is possible to transmit an odd number of half cycles of current to the welding circuit 2.

The operation of the embodiment of my invention shown in the single figure will be explained by considering the system when it is desired to transmit a predetermined number of half cycles of current to the welding circuit 2. The electric valves 4 and 5 are in a nonconducting condition until the high-frequency voltage is impressed on the control members 8. So long as the highfrequency voltage is impressed on the control members 8, the electric valves 4 and 5 are rendered conductive during half cycles to conduct current alternately to transmit alternating current to the welding circuit 2.

The periods during which the electric valves 4 and 5 are rendered conductive depend upon the operative period of the rectifier 22 which, in turn, is controlled by the circuit 40. The voltage impressed on the input circuit 2| of the electric valve oscillator 9 is a rectified alternating voltage and so long as this voltage is present, the control members 8 of electric valves 4 and 5 are energized. Due to the fact that the voltage of circuit 21 is a pulsating voltage, the high-frequency output voltage of the electric valve oscillator 9 is modulated in magnitude in accordance with the input voltage. The spark-gap I8 asassuring positive initiation of arc discharges in electric valves 4 and 5.

The electronic discharge devices 23 and 24 are and resistance 49. There is impressed on the grid 21 of discharge device 23 a voltage equal to the voltage drop across resistance 42 and the upper part of resistance 43. Electronic discharge device connected resistance Of course, when dlstance 48 applied to the grid 21 of electronic discharge device 23 is the voltage difference betveen the voltage drop across resistance 42 plus the upper part and the voltage drop across capacitance 43. At the start of the transient period immediately following the initiation of conduction of electric valve 41, this voltage difference is such as to maintain the grid 21 of discharge device 23 positive. In other words, the transient current transmitted by the circuit inresistance 49 produces across the terminals of resistance 49 a positive transient voltage which renders electronic discharge device 23 conductive. Discharge device 23 is rendered conductive the instant the grid 21 is rendered positive, as the transformer 29 is so polarized that the anode of 23 is positive when electric valve 41 is rendered conductive. Since the voltage across capacitance 48 approaches the voltage total across resistances 42,

43 and 44, as a limit, the voltage applied to the grid 21 of device 23 at the end of the transient period will be negative, thus, again, maintaining discharge device 23 nonconductive. of the transient period during which discharge device 23 conducts is determined by the setting of the slides of resistance 43. In this manner the duration of the period of conduction may be maintained for fixed values of capacitance 4 8 and resistance 49. Of course, control of the period of conduction may be obtained by changing the values of capacitance 48 and resistance 49.

Electronic discharge device 24 follows the electronic discharge device 23 and the rectifier 22 transmits rectified alternating current to the input circuit 2| of the high-frequency oscillator 9. The welding circuit 22 is energized during an interval of time corresponding to the adjustment of the slider of resistance 43.

While I have shown and described my invention as applied to a particular system of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

In combination, an alternating current circuit, a load circuit, electric translating apparatus The portion 1 connected between said circuits and comprising a pair of reversely connected electric valve means of the type employing an ionizable medium and each having an anode, a cathode and a control member of the starting band type, high-frequency means for energizing the control members to render said electric valve means conductive, and means comprising an electric discharge device for controlling said high-frequency means to efiect energization of said load circuit for a predetermined interval of time.

2. In combination, an alternating current circuit, a load circuit, electric translating apparatus r connected between said circuits and comprising a pair of reversely connected electric valve means of the type employing an ionizable medium and each comprising an anode, a cathode and a control member of the starting band type, highfrequency means for energizing the control members to render said electric valve means conductive, and means for rendering said high frequency means operative for a predetermined interval of time to effect energization of said load circuit during a corresponding interval of time.

3. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a pair of reversely connected electric valve means of the type employing an ionizable medium and each comprising an anode, a cathode and a control member of the starting band type, high-frequency means for energizing the control members to render said electric valve means conductive, and means responsive to a predetermined controlling operation for rendering said high-frequency means operative for a predetermined interval of time.

4. In combination, an alternating current supply circuit, a load circuit, electric translating render the electric valve apparatus connected between said circuits and comprising a pair of reversely connected electric valve means each provided with a control member for controlling the conductivity thereof, highfrequency generating means for energizing the control members, means comprising a rectifier for energizing said high-frequency means, and means for controlling said rectifier to effect energization of said load circuit for a predetermined interval of time.

5. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a pair of reversely connected electric valve means each having a control member for controlling the conductivity thereof, a high-frequency oscillator connected to energize the control member, means for energizing said oscillator comprising a full-wave rectifier, and means for rendering said rectifier operative for a predetermined interval of time.

6. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a pair of reversely connected electric valve means of the type employing an ionizable medium and each having an anode, a cathode and a control member of the starting band type, high-frequency means for energizing the control members to render said electric valve means conductive, and discharge means having a predetermined minimum breakdown voltage characteristic and being connected between the high-frequency means and the control members for controlling said high-frequency means so that a steep wave front voltage is impressed on the control members.

7. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a pair of reversely connected electric valve means of the type employing an ionizable medium and each having an anode, a cathode and a control member of the starting band type, high-frequency means for energizing the control members to means conductive and having an output circuit connected to the control members, and a spark-gap connected in said output circuit.

'8. In combination, an electric valve oscillator having an input circuit and an output circuit,

means for energizing said input circuit comprising a source of alternating current and a full 2 wave rectifier comprising a pair of electronic discharge devices each having a control member, said electronic discharge devices being connected to said input circuit, means for impressingon the control member of one of said discharge devices a biasing potential tending to maintain said one discharge device nonconductive, means responsive to the current conducted by said one discharge device for energizing the control member of the other discharge device to render the other discharge device conductive, and means for impressing on the control member of said one discharge device a voltage sufficient to overcome the effect of said biasing potential to efiect energization of said input circuit.

9. In combination, an electric valve oscillator having an input circuit and an output circuit, means for energizing said input circuit comprising a source of alternating current and a full wave rectifier comprising a pair of electronic discharge devices each having a control member, said electronic discharge devices being connected to said input circuit, means for impressing on the control member of one of said discharge devices a biasing potential tending to maintain said one discharge device nonconductive, means responsive to the current conducted by said one discharge device for energizing the control member of the other discharge device to render the other discharge device conductive, and means for impressing on the control member of said one discharge device a voltage sui'licient to overcome the effect of said biasing potential to effect energization of said input circuit for a predetermined interval of time.

19. In combination, an electric valve oscillator having an input circuit and an output circuit,

means for energizing said input circuit comprising a source of alternating current and a full wave rectifier comprising a pair of electronic discharge devices each having a control member, said electronic discharge devices being connected to said input circuit, means for impressing on the control member of one of said discharge devices a biasing potential tending to maintain said one discharge device nonconductive, means responsive to the current conducted by said one discharge device ber of the other discharge device to render the other discharge device conductive, and means for effecting energization of said input circuit for a predetermined interval of time comprising a source of direct current, a voltage divider con nected to said source of direct current, a serially connected capacitance and a resistance energized in accordance with a voltage derived from said voltage divider and an electric valve for effecting transfer of a transient current through said capacitance to impress on the control member of said one electronic discharge device a transient voltage sufiicient to overcome the effect of biasing potential.

11. In combination, a source of low-frequency alternating current, a load circuit, electric translating apparatus connected between said circuits and comprising an electric valve means for permitting the transfer of low-frequency current, a high-frequency current generator connected to render said electric valve means conductive, and means including a capacitance for rendering said generator operative for a time interval depending upon the charging rate of said capacitance.

12. In combination, a source of low-frequency alternating current, a load circuit, electric translating apparatus connected between said circuits and comprising an electric valve means for permitting the flow of low-frequency current to said load circuit, a high-frequency current generator connected to render said electric valve means conductive, and means including a circuit comprising a capacitance for rendering said generator operative for an interval of time depending upon the time constant of said last mentioned circuit.

13. An electric system comprising, in combination, a source of low-frequency current, a load device, circuit means connecting th load device to the current source including a pair of unidirectional conducting valves for permitting the low-frequency current to flow in half cycle increments, both of said valves having principal electrodes, circuit connections in which the potentials of the homologous principal electrodes of said valves are maintained independent of each other, high-frequency current means to inifor energizing the control mern- 5 tiate the flow of low-frequency current to said load device at the time said valves receive energy from said high-frequency current means and means for permitting the application of said high frequency current to be initiated at a time determined by the voltage waves of said source.

1 An electric system comprising, in combination, a source of low-frequency current, a load device, circuit means connecting the load device to the current source including a pair of inversely connected unidirectional conducting valves for permitting successive half cycles of the low-frequency current to new, control means individual to each valve, a high-frequency current generator including a space discharge device provided with an anode, a cathode and a control grid connected to apply high-frequency current to said control means for rendering said valves conducting to permit the flow of low-frequency current to said lead device, a source of energir'ing potential for generator, and means for applying said energizing potential across said anode and cathode for a predetermined interval of time to permit a predetermined number of successive half cycles of the low-frequency current to flow to said load device.

15. An electric system comprising, in combinertlon, a source of low-frequency current, a load device, circuit means connecting the load device to the current source including unidirectional conducting valve means for permitting the lowfrequency current to flow in half cycle increments, a highfrequency current generator con.- nected to render said valve means conducting, and means including a capacitor for operating said generator for a time interval depending upon the discharge rate of the capacitor.

16. Apparatus for supplying power from a source to a load comprising an electric valve having a control electrode for conducting current from said source to said load, means for generating a high frequency potential, means for coupling said high frequency potential generating means to said control electrode to control the conductivity of said valve, means for initiating the operation of said generating means and means for interrupting the operation of said generating means a predetermined interval of time after its initiation.

17. Apparatus for supplying power from a source to a load comprising an electric valve having a control electrode for conducting current from said source to said load, means for generating a high frequency potential, means for coupling said high frequency potential generating means to said control electrode to control the conductivity of said valve, and means for con trolling said generating means in accordance with the voltage of said source.

18. Apparatus for supplying power from a source to a load comprising an electric valve having a control electrode for conducting current from said source to said load, means for generating a high frequency potential, means for coupling said high frequency potential generating a means to said control electrode to control the conductivity of said valve, and means for controlling the operative period of said generating means.

HAROLD W. LORD. 

